I got a question.
If you were in charge of the anime and you were going to have Misty rejoin Ash how would you make her comeback?
I would have Misty's sisters return and be gym leaders again, then Misty tells Ash that she is not gym leader anymore, then Ash decides if she isn't doing anything join him again. Then when Ash is done Unova have him continue on his journey and have Misty as the main character of the show and write off Ash.
Also when she joins Ash she will be wearing a new outfit that would look stunning
Showing that Misty will be leaving and decides to check the Unova. Then wait a few episodes before Ash comes across Misty. The two, with Cilan, goes to crab a bite and ask how each adventures been. Team Rocket comes and do their usual thing. then they go on their usual adventure and Misty just tags along.
OR better yet, Misty could be riding her NEW bike and bump into Ash and Ash broke the bike again. Ash has an addiction of owning Misty another bike! lol